How to determine if a C++ class has a vtable?

For completeness sake, here's the answer my buddy just sent me. From the look of it, it's probably similar to how TR1 does it (though I haven't looked at the code myself).

template<class T>
class HasVTable
{
public :
    class Derived : public T
    {
        virtual void _force_the_vtable(){}
    };
    enum { Value = (sizeof(T) == sizeof(Derived)) };
};

#define OBJECT_HAS_VTABLE(type) HasVTable<type>::Value

The standard method is to use std::is_polymorphic from C++11/C++03 TR1/Boost to determine if a class (and its bases) contain any virtual members.

#include <type_traits>
#define OBJECT_HAS_VTABLE(T) (std::is_polymorphic<T>::value)